std::basic_streambuf<CharT,Traits>::pbackfail
From cppreference.com
< cpp | io | basic streambuf
|
protected
:
virtual int_type pbackfail( int_type c = Traits:: eof ( ) ) ; |
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This function can only be called if any of the following condition is satisfied:
- gptr() is null,
- gptr() == eback(), or
- traits:: eq (traits:: to_char_type (c), gptr( ) [ - 1 ] ) returns false
This function is called by the public functions sungetc() and sputbackc() (which, in turn, are called by basic_istream::unget and basic_istream::putback
1) There is no putback position in the get area (
pbackfail() is called with no arguments). In this situation, the purpose of pbackfail()
2) The caller attempts to putback a different character from the one retrieved earlier (
pbackfail() is called with the character that needs to be put back). In this situation, the purpose of pbackfail() is to place the character c into the get area at the position just before basic_streambuf::gptr()
The default base class version of this function does nothing and returns Traits::eof() in all situations. This function is overridden by the derived classes: basic_stringbuf::pbackfail, basic_filebuf::pbackfail, strstreambuf::pbackfail
Parameters
| ch | - | character to put back or Traits::eof() if only back out is requested |
Return value
Traits::eof()
Example
| This section is incomplete Reason: no example |
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 32 | C++98 | the calling condition '
traits::
eq
(
*gptr(
),traits::
to_char_type
(c)
)
returns false' did not match the description of sputbackc() |
corrected to match the description |
See also
|
[virtual]
|
backs out the input sequence to unget a character, not affecting the associated file (virtual protected member function of std::basic_filebuf<CharT,Traits>) |
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[virtual]
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puts a character back into the input sequence (virtual protected member function of std::basic_stringbuf<CharT,Traits,Allocator>) |
|
[virtual]
|
backs out the input sequence to unget a character (virtual protected member function of std::strstreambuf) |
| moves the next pointer in the input sequence back by one (public member function) |
|
| puts one character back in the input sequence (public member function) |